1. Field of the Application
The present invention relates to the field of welding engineering, and more specifically, to methods for electroslag welding of structural elements with large weld areas, particularly with a weld thickness of over 30 mm.
The invention is readily adapted for application in welding light metals (the term "light metals" is used herein to denote metals the density of which is less than that of fluxes used for their welding). In particular, the invention may be effectively employed in chemical, metallurgical, electrical-engineering and other enterprises in welding large cross-section elements of aluminum, titanium, copper, and alloys thereof, as well as of magnesium alloys and of various steels.
There is a trend nowadays for intensifying production processes by increasing the capacities of individual units which is also characteristic for production of aluminum, chlorine, and other products by electrolytic processes, where a need for considerably increasing the process current thus arises. This involves employing large-size aluminum buses with a metal thickness as great as 160 mm and more as current conducting elements. In this case the quality of welded contacts is of prime importance. A similar situation is also typical for structures of other metals and in other fields of engineering.
As a consequence, large-thickness metal finds an ever increasing application in manufacturing welded structures.
It is well known that aluminum, magnesium, alloys thereof, and other metals of a large thickness are at present welded using various multipass arc welding methods. However, the efficiency of welding and the quality of welded joints fall drastically as the thickness of the metal being welded is increased. This stems from an unavoidable necessity of dressing every built-up layer before the next pass. Moreover, multipass welding necessitates turning over many times the elements being welded in order to retain the geometrical shape thereof. And, finally, the use of said methods leads in most cases to anisotropy of the weld metal properties.
This has created an acute problem of welding large-thickness structural elements of such metals as magnesium, aluminum, alloys thereof, and other metals with provision for both high efficiency of welding and high quality of welded joints.
This problem could be adequately solved by a prior-art method of electroslag welding (cf., e.g. U.S. Pat. No. 3,885,121 and F.R.G. Pat. No. 1,917,861). The method of electroslag welding of metals is generally implemented with the aid of a molding means comprising an inlet pocket for starting the welding process, withdrawal plates for withdrawing a shrinkage cavity and a slag both from the gap, and side molds. The pocket for starting the process is arranged beneath the gap defined by the edges being welded, and the withdrawal plates, above the gap. A slag bath is established in the pocket, which is followed by feeding therein an electrode material in the downward direction. Molten metal descending onto the bottom of the slag bath, forms the weld in the upward direction. The electrode is melted by the heat of the slag bath through which the welding current is passed.
The prior-art electroslag welding methods are, however, applicable only for metals whose density greatly exceeds that of the welding flux, and are unfit for welding light metals due to the fact that in this case molten metal is less dense than slag and floats therefore to the surface of the slag bath. This upsets the stability of the process, is accompanied by shorting the welding circuit and other adverse effects. This is especially encountered in electroslag welding of aluminum and its alloys, whose density differs but little from that of welding fluxes, while such metals as magnesium and its alloys altogether fail to be welded by prior-art electroslag welding methods.
The principal object of the invention is to provide a method for electroslag welding of light metals, i.e. metals whose density is less than that of the welding flux.
One more object of the invention is to provide a method for electroslag welding of light metals, which ensures stable run of the process, high quality and operating reliability of weld joints.
Another object of the invention is to enhance the efficiency of welding light metals.
Still another object of the invention is to provide a method for electroslag welding of various type structural units whose element edges to be welded are substantially of any cross-section and configuration.
A further object of the invention is to provide a method for electroslag welding in the downward direction.
Still further object of the invention is to provide a method for electroslag welding of light-metal structures with a restricted access thereto from above for carrying out mounting jobs.